Manufacture of perborates



' No Drawing.

UNITED STATES PATENT OFFICE.

JOHA NN KONRAD LANGHARD, OF FREDRIKSSTAD; NORWAY, ASSIGN'ORTO FRED- IRIKSSTAD ELEKTROKEMISKE FABRIKER A/S, OF FREDRIKSSTAD, NORWAY.

MANUFACTURE OF PERBQRA'IES.

To all w from it may 0072 06m Be it known that I, JOHANN KoNRADLANGHARD, a citizen of Switzerland, residing at Fredriksstad, Norway,have invented certain new and useful Improvements in the Manufacture ofPerborates; and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

This invention relates to the manufacture of perborates by theelectrolysis of aqueous borate solutions and has for its object animproved method of treating the electrolyzed solution.

A known method of producing sodium,

perborate electrolytically.consists in electrolyzing a solutioncontaining borax and soda (sodium carbonate).

In this process the sodium carbonate is gradually neutralized tobicarbonate in proportion to the formation of perborate.

The reactions taking place may be illustrated by the equation:

It has been ascertained that it is of importance to reconvert theresulting bicarbonate into carbonate in order to attain an advantageouscurrent output. This may be effected by means of caustic alkali (NaOH)or lime.

It is an important condition of a satis factory output, however, thatthe substances referred to are introduced in a state in which they arepractically free from catalyzers. To use chemically pure hydroxide ofsodium is of course not practicable, while on the other hand thecommercial product usually contains small quantities of iron or evenmanganese compounds. The same applies also to lime. Under theseconditions the industrial value of the process is rather questionable.The present invention has for its object a process whereby thedifiiculties re ferred to are eliminated by simple and suitable means.

According to the invention the electrolyzed solution is treated with aperoxide instead of the hitherto employed substances, caustic soda orlime. Sodium peroxide is manufactured in a very pure conditionpractically free from injurious constituents and Specification ofLetters Patent. Patented Feb. 28, 1922. Application filed Febrnary G,1920. Serial No. 356,650.

when added to the electrolyzed solution it will have no disadvantageousinfluence upon the result. l

The action of the sodium peroxide may be illustrated by the followingequation:

The addition of the peroxide also results in the formation of additionalquantities of perborate as shown by the equation.

Experiments have proved that the precipitation of perborate by theaddition of the peroxide is much more abundant than that obtained bycooling the electrolyte. The advantages of the described process and itspractical value are obvious.

Example: A hundred liters of an aqueous solution containing 40 g. boraX,100 g. soda, 7 g. perborate of sodium in the litre, and which mayconsist of the mother liquor from a previous operation is subjected toelectrolysis in a suitable apparatus with a current strength of forinstance 120 amp. during for instance 4 hours. During the electrolysisthe content of perborate will increase for instance to 12 g. ofperborate in the litre. without crystallization taking place. At thesame time an equivalent quantity of sodium bicarbonate has been formed.To the liquid is now added sodium peroxide in a quantity of for instanceg. This addition of sodium peroxide on the one hand effects regenerationof carbonate and on the other hand results in such an increase in thepercentage of perborate, that percipitation of sodium perborate willbegin. After some hours the crystallization of sodium perborate will befinished, without any considepable cooling of the liquid having takenace.

p The solution can now be subjected to electrolysis for the productionof further quantities of perborate, it may be after having been suppliedwith an additional quantity of borax.

The described treatment of the solution is suitably carried into effectin a separate ves sel into which the solution is conveyed from theelectrolytic cells. When the precipitated perborate has been separatedfrom the solution, this latter can be introduced into an electrolyticcell for further treatment.-

Claims 1. Process for the manufacture of sodium perborate, comprising incombination the steps of electrolyzing a solution containing hora-xandsoda and adding sodium peroxide to the electrolyzed solution.

2. Process for the manufacture of sodium perborate comprising the stepsof subjecting a solution containing borax and soda toel'ec trolysis,adding sodium peroxideto the elec trolyzed solution, separating theprecipitated presence of two subscrlbmg witnesses.

sodium perborate from the solution and subjecting thesolution toelectrolysis.

3. In a process of manufacturing sodium perborate, which consists inelectrolyzing a solution containing borax and sodium car,-

solution, thereby increasing the yield in sodium perborate andregenerating the solution in sodium carbonate. g V

In testimony that I claim the foregoing as my invention, I have signedmy name in JOHANN KONRAD LANGHARD. l Vitnesses:

NATE. A. HEDENsoi-IoN, R BERT H. FRAZTER;

